BSA B25
"B25SS"
|
|
Make Model | BSA B25, B25SS, B25T & B25 Fleetstar |
Year | 1968 - 70 |
Engine | Single, OHV, 4-sroke |
Capacity | 249 cc / 15.2 cub in |
Bore x Stroke | 67 x 70 mm |
Cooling System | Air cooled |
Compression Ratio | 10:1 Fleetstar only: 8.5:1 |
Lubrication | Wet sump |
Oil Capacity | 2.25 L / 4.8 US pints |
Exhaust | Twin, stainless steel and chrome |
Carburetor | Amal Concentric 928/20 |
Ignition | Coil |
Spark Plug | Champion N3, 0.50 - 0.65 mm gap, 14 mm thread |
Battery | PUZ5A, 12 V, 10 Ah |
Starting | Kick start |
Clutch | Multi-plate with integral cush drive |
Transmission | 4-Speed constant mesh |
Final Drive | B25SS, Fleetstar: Chain, 106 links, Reynolds 110 054 B25T: Chain, 107 links, Reynolds 110 054 |
Overall Gear Ratio | B25 SS, Fleetstar: 1st 18.33 / 2nd 11.35 / 3rd 8.60 / 4th 6.92:1 B25T: 1st 19.48 / 2nd 12.06 / 3rd 9.14 / 4th 7.35:1 |
Maximum Power | 19 kW / 25.8 hp @7250 rpm |
Frame | Loop frame with single down tube with double cradle for engine |
Front Suspension | Coil spring, hydraulically damped |
Rear Suspension | Girling coil spring, hydraulically damped |
Front Brakes | B25 Fleetstar: 8 x 1.5 in., twin leading shoe, drum B25SS, T: 6 x 0.875 in., single leading shoe, drum |
Rear Brakes | 7 x 1.125 in., single leading shoe |
Wheels | Steel, spokes |
Front Rim | B25SS, Fleetstar: WM2 x 18 B25T: WM1 x 20 |
Rear Rim | B25SS, Fleetstar: WM2 x 18 B25T: WM3 x 18 |
Front Tyre | B25SS, Fleetstar: 3.25 x 18 in. B25T: 3.00 x 20 in. |
Rear Tyre | B25SS, Fleetstar: 3.50 x 18 in. B25T: 4.00 x 18 in. |
Dimensions | Lenght: 2160 mm / 85.0 in. Width: 737 mm / 29.0 in. Height: 1105 mm / 42.5 in |
Wheelbase | 1370 mm / 54 in. |
Ground Clearance | B25SS, Fleetstar: 178 mm / 7 in. B25T: 190 mm / 7.5 in. |
Seat Height | 810 mm / 32 in. |
Wet Weight | B25SS, Fleetstar: 131.5 kg / 290 lbs B25T: 130.2 kg / 287 lbs |
Fuel Capacity | B25SS, Fleetstar: 13.5 L / 3.5 US gal B25T as well as US models: 9L / 2.5 US gal |
Top Speed | 135 km/h / 84 mph (approximately) |
Review | Rider Magazine |
Review of the BSA B25 Starfire
This little machine was an anomaly when it appeared on the showroom floors in 1968; though it was a rather attractive motorcycle, it was powered by an old-fashioned single-cylinder OHV engine.
BSA had been building 250 singles since 1938, and some dim bulb up in marketing thought there was still a market for a little plodder…if you dressed it up real pretty.
It was a tough engine, slightly undersquare with a 67mm bore, 70mm stroke, having an aluminum alloy head and barrel, with an iron liner, a one-piece forged crankshaft with two flywheels running to keep the vibration down, and a duplex-chain primary drive to handle all that power going to the four-speed tranny. The factory claimed over 20 horsepower at 8,250 rpm—perhaps at the piston dome, but certainly not at the rear wheel.
In 1968 quarter-liter bikes were still popular but as sport rather than utility vehicles. Just about every manufacturer had one or two. Lots were two-strokes, like the Montesa Scorpion and Bultaco Metralla singles, or the Yamaha Catalina and Kawasaki Samurai twins, and a few four-stroke singles, like Ducati’s Mark 3 Desmo, Benelli’s Barracuda, Harley’s Aer-macchi 250 with a race-bred pushrod engine, and the rather unexciting British offerings, the Triumph TR25 and BSA Starfire. Those last two were very similar machines, differing only in styling and badges.
Since this was essentially a BSA product, we should take a look at its genesis. That 1938 C10 was a flathead engine with separate gearbox in a rigid frame, and after the war an OHV C11 version soon became available, in either a rigid or a plunger frame. The C12, appearing in 1956, used a swingarm frame. 1959 was the year of big change, with a unitized engine/transmission in the C15 Star. In best British tradition the crankcases were split vertically, which usually meant leaving drops of oil wherever the bike was parked. A 26mm Amal Monobloc carb was fitted.
"B25T"
The very first Starfires to come into this country had the old skinny seven-inch brake drums on both 18-inch wheels, but that was soon changed to a full-width drum on the front. The frame was little changed from the C15, though the fork was improved with a double hydraulic damping system. And the metal covers protecting the sliders had now given way to sporty rubber gaiters! Yes, yes! The shrouding had come off the shock absorbers as well. And the rather dull oblong gas tank became an artfully contrived fiberglass container holding 2.5 gallons of fuel, with glorious sunburst BSA emblems. High test, please, as that compression ratio needed the best. Abbreviated chromed fenders and sculpted side panels and oil tank finished the new look, along with the chrome headlight shell and Smiths speedometer (missing on this one). Very pretty it was, in blue and white.
Click down into first, the cush drive in the clutch smoothes the take-up, and away you motor. In-town work is a bit sluggish as the cam does not really function well at under 4,000 rpm. The fork has over five inches of travel, the shocks almost three, but the springs are on the stiff side of plush. If the road is smooth, the ride is comfortable. Now the oil is warm and you are in the country. If you are a sporting person, you might have sprung for the optional tachometer, but if not, the engine will certainly tell you when it is near the 8,000 rpm line. The speed tops out at almost 80 mph in fourth gear; you are exhilarated and consider the $750 well spent. That is until a Suzuki X-6 250 Hustler blasts by you, shifting into sixth gear at 90 mph; that bike cost less than $700.
Article by Clement Salvadori, 2007
"B25 Fleetstar" |